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Information About Age-Related Macular Degeneration
Eye Anatomy
When light enters the eye, it is focused by the cornea and the lens onto the retina. The retina is the delicate innermost layer of tissue that lines the back of the eye. It contains various layers of light-receiving or photoreceptor cells that are directly connected to the brain by the optic nerve. If you think of the eye as a camera receiving images, then the retina is the film where those images are recorded for the brain to interpret. 
The macula is a very small area of the retina that is responsible for central vision and color vision. The macula allows us to read, drive, watch television, recognize faces and perform detailed work. The center of the macula is called the fovea; this is the point of visual fixation (what we look directly at). Surrounding the macula is the peripheral retina which is responsible for side vision and night vision. If the macula deteriorates for some reason, the retina becomes like a camera with a spot on the film; the center of the field of vision blurs and detail is lost.
Age-related Macular Degeneration (AMD)
Like other parts of our body, our eyes change as we age. Some amount of deterioration of the macula is a natural result of this aging process. Even so, many people maintain reasonable vision throughout their lifetime while others lose vision as they get older. Accelerated deterioration of the macula can also be caused by a variety of conditions, such as injury, infection or inflammation, or it can be caused by a degenerative condition known as Age-related Macular Degeneration (AMD).
Because AMD affects central vision, the most common symptoms are blurring of central vision and difficulty seeing details. There may be blind spots, resulting in dark or empty areas in the center of vision. Patients may also notice distortion of lines and shapes; for example, a window or door frame may not look square, or sentences on a page may look wavy, or parts of the vision may be missing (for example, words might seem to disappear on the page when one tries to read smaller print). Color vision may also be diminished. AMD has two basic types, wet and dry.
The wet form of AMD, also called exudative (eAMD), occurs when abnormal blood vessels begin to grow beneath the macula. These new blood vessels are fragile and may leak fluid or blood, causing the choroid to deteriorate. Fluid and blood then enter the macula and cause photoreceptor cells to degenerate. These blood vessels may also develop scar tissue which destroys the retina. If left untreated, the bleeding and scarring will lead to a profound permanent loss of central vision with vision loss progressing rapidly. Wet AMD accounts for about 10% of severe vision loss.
The dry form of AMD, also called atrophic or non-exudative (aAMD), is characterized by a loss of the pigmented cells that support the macula. This loss results from the build-up of drusen, which are small yellowish fatty deposits that accumulate beneath the macula. These deposits block nutrition from reaching the retina, which interferes with the pigmented cells or retinal pigment epithelium (RPE) and the photoreceptors. Over time, these cells degenerate and die. These changes result in a distortion of central vision that is most apparent when reading. Dry AMD usually progresses more slowly than wet AMD, and may cause loss of central vision. Dry AMD accounts for about 90% of cases.
If you suspect you are experiencing symptoms similar to those for either the wet or dry form of AMD described above, see your eye care professional for an evaluation as soon as possible. For additional information on how you can check for AMD and some of the methods that your doctor might use, see our page "Methods of Checking for AMD."
Reducing the Risk of AMD
At present, there is no cure for AMD. Studies, however, suggest that the risk of developing AMD can be lowered with changes in lifestyle and diet, including:
- Quitting smoking and avoiding second-hand smoke.
- Eating a well-balanced, low fat diet, including regular servings of fish.
- Avoiding excessive sunlight exposure by wearing sunglasses and a hat.
It has not yet been clinically proven that taking vitamin supplements can replace the nutrients found naturally in food sources. However, if a balanced diet is not followed, a multivitamin is generally recommended. Dangerous side effects can occur when high doses of some supplements are consumed, so consult your physician prior to starting a regimen of high dose vitamin supplements (see Vitamins and Age-related Macular Degeneration).
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